In modern integrated circuit semiconductor manufacturing, etching is a process used to pattern circuits on a semiconductor. Plasma etching is one type of etching process, in which a high-speed stream of ions is directed at a wafer. The ions etch the surface of the wafer, thus modifying the wafer's physical topography and allowing the creation of a pattern. Plasma etching apparatuses typically include a plasma chamber and an electrostatic chuck (ESC) residing within the plasma chamber.
The ESC is a device that employs electricity to generate electrostatic forces, such as Coulombic and Johnson-Rahbek Forces, that hold the wafer in place in the plasma chamber while the wafer is processed. ESCs typically include a base member, which acts as an electrode, a top member composed of a dielectric, and some bonding medium between the two layers. Other types of ESCs include a secondary conductive pole insulated from the base member by a dielectric coating that substantially covers the conductive pole and base member. Many modern ESCs use a gas as a heat-conductive material. The gas is supplied through the ESC surface to transfer heat between the wafer and the ESC to control wafer temperature during the etching process.
During the plasma process, the plasma chamber in which the ESC resides fills with plasma and plasma by-products (products of the reaction between the plasma gas and the wafer surface). The plasma and plasma by-products may cause the ESC to deteriorate in a process known as plasma etching or process gas erosion. Another factor that may contribute to the deterioration of ESCs is the installation and removal of process kits. Some process kits surrounding the ESC in the chamber may abrade the ESC sidewall when the kits are installed and removed. Parts abrasion refers to the breaking away of various elements of the ESC, such as the bonding medium between the top member and the base member or the dielectric covering of the base member. The introduction of these particles into the plasma chamber contaminates the plasma chamber and the wafer presently being processed.
Parts abrasion may occur where the top member joins the bottom member and the areas on the side of the ESC that are near components that conduct electricity. As these areas wear down, the heat transfer gas escapes without carrying heat away from the wafer, and electricity arcs between the internal components of the ESC, reducing the holding force of the ESC. Ultimately, the problems of gas leakage and edge arcing shorten the useful life of the ESC.
One attempt to prevent deterioration of ESCs involves the application of epoxy to the ESC in areas prone to parts abrasion. Applying epoxy to these areas slows down ESC deterioration, but the epoxy is not resistant to parts abrasion caused by the plasma or plasma by-products, and as a result, gas leakage and edge arcing may continue to occur. In addition, application of epoxy to the ESC is permanent, making it difficult to refurbish the ESC as the epoxy or other elements of the ESC deteriorate. Therefore, there is a need for an improved electrostatic chuck to overcome the above-described and other shortcomings in the prior art.